1. Field of the Invention
The present invention relates to wireless radio equipment. More particularly, though not exclusively, the present invention relates to a method and apparatus for providing improved quadrifilar helix antennas.
2. Problems in the Art
Some antennas, such as satellite antennas, require circular polarization because the orientation of the user with respect to the satellite is not usually predetermined. Circular polarization is typically independent of orientation. Few antennas are suitable for circular polarization, especially for use with handheld wireless equipment. Three types of prior art circularly polarized antennas include turnstile antennas, patch antennas, and axial mode helical antennas. The turnstile and patch antennas are not suitable for use with handheld equipment because the antennas are larger than desired. Axial mode helical antennas are not suitable for use with handheld equipment because of the excessive diameter of the antenna.
The most desirable type of circularly polarized antenna is a quadrifilar helix antenna. To meet beamwidth and size requirements for personal satellite communications, quadrifilars are made with 1/2 turn, 1/4 wave elements. Hybrid power dividers are required to establish the phase between elements of the quadrifilar helix antenna. However, hybrid power dividers require more space than is desirable. Therefore, there is need for a quadrifilar helix antenna which does not require hybrid power dividers.